The present invention relates to a clutch brake arrangement for farm working machinery etc., and more particularly to a clutch brake arrangement for farm working machinery etc., which causes smooth and reliable movement of a pressure plate toward an output shaft in a simplified manner, reduces as much as possible the amount of a load applied on an engine when the engine is switched from idling over to clutch engagement, assures smooth clutch engagement with no fear of an engine stop, allows clutch disengagement and braking by release of an operating rod, and is of small size and light weight.
For example, when a power-operated lawn mower is moved to cut the grass in varied places, it is required to stop the rotation of a cutting tool while idling an engine to save the labor involved in re-actuation of the engine and for safety's sake.
The conventional clutch brake arrangements known in the art typically include an engine mount, a cam plate fixed to the engine mount and a cam plate cover rotatable by an operating rod. The cam plate and the cam plate cover are fitted over an output shaft in an opposite manner. A cam ball is received in a ball clamp having opposite inclined faces. When the operating rod is turned in its operating direction, the cam plate cover moved away from the cam plate by the rolling movement of the cam ball. A pull is then given to a pressure plate biased toward a rotary member and engaged with a lining plate by a brake spring, whereby the lining plate is engaged with the clutch disc for unison rotation of the rotary member and the clutch disc. On the other hand, release of the operating rod causes the pressure plate to move by the brake spring, thereby to give a push to the lining plate. As a result, the lining plate disengages the clutch disc for braking, and the cam plate cover toward the cam plate, and returns to the initial position.
According to the known arrangements, the movement of the pressure plate toward the output shaft can be achieved in a simple manner. Furthermore, smooth clutch engagement is assured with no fear of an engine stop, since it is possible to reduce as much as possible the amount of a load applied on the engine when it is switched from idling over to clutch engagement. To add to this, clutch disengagement is effected by release of the operating rod for braking.
However, these arrangements have a disadvantage that their overall size increases in the direction of axis of the output shaft, since the mechanism for engaging or disengaging the lining plate with or out of the clutch disc rotating with the output shaft is fitted over the output shaft extending from the engine mount. Care should also be taken to cause smooth and reliable parallel movement of that mechanism along the axial direction of the output shaft.
In order to prevent grass, weeds, earth and sand as well as mud from entering the arrangements, a dust cover is further provided to close up the gaps therein. Nonetheless, it is likely that such matters may enter the arrangement from small gaps, and accumulate therein so that the smooth operation of a cam mechanism is disturbed. Furthermore, the assembling of the dust cover is complicate, troublesome, etc.